This invention relates to collapsible and expandable tubular structures, and more particularly to a curtain comprised of flexible strips made into tubular units by bands of adhering contact. The tubular structure can be used as an insulating curtain over openings such as doors, windows and the like. The invention also relates to the method of producing such curtains from continuous strips of thin-film material.
Flexible insulating curtains having tubular units, along with methods of making such structures, are known in the prior art. One such curtain is found in U.S. Pat. No. 4,019,554 and a method for making that curtain is found in U.S. Pat. No. 3,963,549. However, such prior art curtains require relatively narrow tubular foils of 2 to 3 inches in diameter and use a single band of adhesive between adjacent foils. As winding speed is limited by the rate at which adhesive can be applied to the foil, the prior art method is quite slow. Furthermore, the curtain produced has only one tubular thickness.
A beehive like wall structure with multiple cells for insulating purposes is illustrated in Finnish Pat. No. 23939 of May 31, 1950. The structure is made by gluing thin plates of paper to each other and to outside surface boards at areas of contact on alternating sides of the plates. Although the cellulated structure can be pressed together for transporting and expanded for installation, the insulation board has relatively few cells in each row and those cells could be compressed and expanded only a few times without deterioration of the wall material. According to this patent, the area of glued contact between adjacent plates must be limited to a maximum of 1/3 of the width of the air cell, presumably to minimize the severe distortion that would occur in the walls of the partial cells adjacent to each surface board. Since the width of the glued area is transverse to the direction in which insulation is desired, the air cells must be fully expanded for effective insulation.
Such disadvantages and limitations of the prior art are overcome by the tubular structure of the present invention which may have a plurality of insulating cavities both in the direction of curtain height and in the direction of curtain thickness. While the insulating properties of one tubular unit are significant, much better insulation can be provided by a plurality of tubular units across the curtain thickness. The insulating characteristics of those units are further enhanced by aligning the bands of adhering contact in the direction to be insulated. The insulating effectiveness of the tubular cavities is thereby maximized and does not change significantly with the degree of expansion.
The novel method disclosed for producing insulating curtains is much simpler and faster and more economical than heretofore known. A plurality of curtains are simultaneously produced from strips of relatively inexpensive material. The individual strips may be of any thin flexible material, and are preferably of thin film plastic. Although narrow relative to length, the strips may be many feet in width, the width being limited only by practical considerations of winding sheet material.
In practicing the method, two or more strips are pulled simultaneously from multiple sources and each passed through a station at which adhesive is applied to one surface in multiple transversely spaced bands. The bands are applied in a staggered relationship and the strips arranged adjacent to each other with an adhesive surface opposing a non-adhesive surface. The bands are preferably of a substantially uniform width and spaced transversely from each other at substantially the same distance. The width of each band corresponds to the desired width of the corresponding tubular unit in its expanded state. Accordingly, the sum of the width dimensions of all bands spaced transversely across two adjacent strips will equal approximately the overall thickness of the curtain when fully expanded.
After application of the adhesive bands, the strips are interleaved and wound in superimposed layers about the periphery of a forming member so as to interlaminate adjacent strips and the bands of adhesive there between. The staggered bands between successive strips produce tubular units formed with a lower wall from one layer and an upper wall from the next superimposed layer. The upper and lower walls are adheringly secured together by bands of contact on opposite sides of the tubular cavity and each tube thus formed is adheringly secured to the next superimposed tube by a band of contact across a midsection of the upper tube wall. The side bands and the mid band all extend longitudinally along each tube and define non-adhering sidewalls therebetween. Tubular units so arranged will expand or open when stretched in a direction transverse to the plane of the strips.
As used in this specification, a row refers to tubular units aligned with curtain height and not to successive units in the direction of curtain thickness. For a single row of tubes, the minimum number of transverse bands is 3, additional bands being spaced transversely depending upon the number of adjoining tube rows desired. The number of layers wound upon the forming member is chosen to yield the desired number of tubes in each row, which in turn determines curtain height. The interlamination of only two strips is also possible and will produce tubular units adjoined by bands of contact across the width of the strips. Thus, the curtain may have successive tubular units adjoining in the direction of curtain height or in the direction of curtain thickness or in both directions, the latter being preferred.
After winding is complete, the resulting stack of superimposed tubes is cut transversely, removed from the forming member, and straightened into a linear stack. Where the length of the tubes is a multiple of the desired curtain width, a corresponding number of transverse cuts are made to produce multiple curtains. Where there are 3 or more adjoining rows of tubes, a plurality of curtains can also be produced by one or more longitudinal cuts down the tube length.
After straightening, the strips at the top and bottom of the stack may be pulled apart to expand the tubes. The curtain is extended to its full height when the tubes are fully expanded. The end strips may then be moved together to collapse one or more tubes. The tubes collapse in accordion fashion along fold lines formed by the side bands of contact. When flattened, the height of the tube stack approximates the total thickness of the superimposed layers of film material. To facilitate manipulation of the curtain, one end may be secured to a mounting slat and the other to a second slat movable relative to the first. Pull cords and other conventional hardware may be added to the slats to mount the curtain and selectively collapse and expand the tubular units in a manner similar to venetian blinds.
The invention has many additional objects, some of which are set forth here. The tubular structure can be readily mounted, with or without supporting slats along the end strips, in a number of different positions for a wide variety of uses. It has wide utility as a thermal insulating curtain and when extended vertically can serve as a substitute for storm windows, storm doors and the like. The curtain can be extended horizontally and pulled taut to serve as insulation beneath a floor or above a ceiling. The individual tubes can be collapsed and expanded numerous times and provide a curtain having a long usable life. In its collapsed state, either as mounted or as removed for storage, the curtain folds into a stack of thin flat strips neatly aligned in a column.
Curtains of varying height can be made depending upon the number of strips superimposed upon the forming member. Multiple curtains of less height than originally formed can also be made by cutting the linear stack of tubes longitudinally in a direction transverse to curtain height.
The composition of the strip material may be selected to yield light admitting tubes (transparent or translucent), light absorbing tubes (black or other dark colors), or light reflecting tubes. A pigment material may also be added to the adhesive used so that the bands of contact have similar light controlling characteristics. With light controlling bands, the degree of light admitted, absorbed or reflected can be controlled by tilting the upper and lower most strips by means of attached slats which will in turn produce a corresponding tilt of the longitudinally extending bands in a manner similar to the louvers or slats of a venetian blind. Similar light controlling characteristics can be obtained by applying appropriate coatings to one or more sections of each tube wall.
The tubular structure has many other applications, such as structural members for greenhouses and other buildings requiring the admission of large amounts of light and for modular structures utilizing flexible sheet material. The tubular units may be reinforced internally and positioned on end as self-supporting walls, folding doors and other structural components. The tubes may also be sealed and pressurized internally with air as structural members for air supported domes and the like.
Numerous other objects and advantages of the invention will be apparent to those skilled in the art from this specification and the attached drawings .